Coating for glass surfaces



June 5, 1928.

1,672,857 H. D. BLAKE Er AL COATING FOR GLASS SURFACES Filed Feb. 27. 1922 INS-CENTER 5:

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Patented June 5, 1928.

UNITED STATES 1,672,857 PATENT OFFICE.

HAROLD D. BLAKE, OI CLEVELAND HEIGHTS, AND JOSEPH E. STONE, OF CLEVELAND, OHIO, ASSIGNORS 130 GENERAL ELECTRIC OOIPANY, A CORPORATION OF NEW YORK.

COATING FOR GLASS SURFACES.

Application lied February 27, 1822. lerlal Io. 589,506.

Our invention relates to processes for coating glass surfaces and to articles produced thereby. More particularly our invention relates to processes for coating lass surfaces which in use are subjected to eat, and has particular application to a coating for incandescent electric lamps.

The objects of our invention are to produce a coating which will adhere the glass surface, which will stand heat without discoloration, and which will also resist the action of water, hot or cold. One of the principal advantages of our invention is that it furnishes an acceptable substitute for sand blasting, which is very objectionable from a sanitary standpoint.

Our invention from one standpoint comprises the application to a glass surface, such as that of the bulb of an incandescent lamp, of a coating comprising kaolin or china clay in a colloidal state. This colloidal state may be produced by the use of a binder consisting of an alkaline silicate such as commercial sodium silicate which ordinarily contains a certain amount of free alkali, or a purer sodium silicate low in free alkali may be used, and a certain amount of alkali such as caustic soda added to the solution. When such a coating is applied as by spraying upon the glass surface and allowed to dry, it produces a very effective coating.

Our invention, from another standpoint, comprises the application to the lass surface of a mineral body material mlxed with an inorganic binder such as sodium silicate, and the subsequent fixing of said coatin by a suitable bath. Materials which have een found to serve well as bod materials are French chalk or talc and china clay or kaolin. These may be used alone or with coloring materials such as zinc oxide (Zn 0) which produces a desirable white. When a thin coating of this kind is applied a very satisfactory substitute for the frosted lamp is obtained. Heretofore it has been ound necessary when such materials have been used for coatings to apply some sort of a protecting or retaining material such as a varnish. This has been more or less objectionable on account of flaking off of the varnish, and also on account of its low resistance to heat. We have found that by fixing the aforesaid coating by subjecting it to the action of materials such as the halogen com- One mixture which we have used is:

French chalk 500 grams. Zinc oxide 500 grams. Sodium silicate (sp. g. 1.375) 1000 cc.s. \Vater 800 cc.s.

The French chalk and zinc oxides are first mixed thoroughly and placed in a ball mill. The sodium silicate solution is then added and the mixture is ball milled, preferably, from 18 to 24 hours.

Another mixture which we have used to produce an appearance similar to that produced by sand blasting comprises:

20 grams white china clay or kaolin, 160 cc.s water, 220 cc.s sodium silicate (sp. g. 1.375). This is ball milled for 14 hours.

Still another mixture is:

White china clay 750 grams. Sodium silicate (sp. g. 1.375)

(low in Na O) 1900 cc.s. Caustic soda grams.

We prefer to dry a coating produced by the application of one of the above mixtures for about three minutes at approximately 150 C. after which the coating is fixed, by applying a suitable solution. Such a solution may consist of a saturated solution of sodium bi-fluoride. Another solution which may be used is as followsz Ammonium chloride crystals 100 grams. Sulphuric acid (C. P. sp. g.

1 84 100 cc.s.

900 cc.s.

Still another solution which may be used consists of:

DiS'tiHJv JJtEZIIIIIII:

300 grams sodium chloride, 1000 cc.s water 80 cc.s concentrated sulphuric acid.

in the accompanying drawing we have shown diagrammatically an a paratus which may be used in the practice 0 our invention. Figure 1 is a diagrammatical view of such an apparatus in side elevation. Figure 2 is an elevation partly broken away showing the spraying portion of the apparatus.

As shown in the drawing, our invention is applied to the coating of incandescent ten seconds.

electric lamps. Such a lamp 10 is mounted in a suitable holder at position A, said'holder being carried on an endless chain 11 which travels in the direction shown by the arrow in Figure 1. At the spraying position B the lamp is suitably spraye while being rotated by means of any suitable spraying device comprising a nozzle 12. The rotation of the lamp during the spraying may be secured in any suitable manner, for instance as shown in Fi re 2, by the friction drive 13. After t e coating has been applied evenly over the whole lamp or any desired portion thereof, the lamp passes into an oven 14 which is heated in any suitable manner. Preferably the heating is at about 150 C. and takes about two minutes. This thoroughly dries the coating. The fixing solution is ap lied at position C. Preferably the fixing solution at 30 to 75 centigrade is contained in a tank 15 which is raised in a suitable manner so as to cause the bulb 10 to be immersed in the fixin solution contained therein. The bulb shoul be kept in the solution for about About one liter of solution for each one hundred incandescent lam s of the 25 watt size or for smaller lamps s ould be used. For larger lamps about one liter for each fifty lamps will give good results.

The lamp next asses 'to position D where a rinsing tan 16 containing water is raised so as to allow the lamp to pass throu h the'water. This washes ofi the sur-' lus xing solution. At position E the lam is dried by means of a suitable heater 17 and while in this osition the lamp may be rotated so as to acilitate the drying. At position F the lamps are removed from the carrier.

What we claim as new and desire to secure by Letters Patent of the United States, 1s

1. The process of coating a glass surface which consists in applying thereto a coating comprising a mineral body material intimately mixed with an alkaline silicate binding material, drying the coating thereon, and thereafter'subjecting the same to the action of a fixing solution containing a halogen compound.

2. A bulb for an incandescent electric lam ly of a er and precipitated silica.

3. The process of aflixing a coatin to a siliceous article comprising applying thereto a preparation containing a soluble silicate, drying said applied preparation and applying a second preparation which re-acts with the first preparation.

4. The process of afiixing a coating to a glass article which comprises appl ing thereto a preparation containing a bo y material mixed with a soluble silicate, drying said preparation and thereafter appl ing a second preparation which re-acts with the first preparation to precipitate silica therefrom.

5. An electric lamp bulb having a coatin comprising an insoluble mineral compoun and preci itated silica.

6. An e ectric lamp bulb having a coating comprising an insoluble silicate and precipitated silica.

In witness whereof, we have hereunto set 85 our hands this 21 day of Feb. 1922.

HAROLD D. BLAKE. JOSEPH E. STONE.

a coating consisting substantia 

